Macrophomina phaseolina (MP) (Tassi) Goid is an agronomically important, soil born, ascomycete fungal pathogen that has a host range over hundreds of plant species including many important economic crops. This fungus has a historical presence in the Southern soil, hence, the potential damage from MP is one of the biggest risks facing the sweet potato industry in the United States. Visual identification of this fungal infection, using their black melanized microsclerotia, is not enough to prevent spreading of the fungus which leads to the need for a rapid diagnostic mechanism for early-stage identification of the fungal infection. Rhizopus soft tissue is another major fungal threat in large-scale sweet potato storage warehouses. Volatile biomarkers for early detection were identified for both these fungi. Here we present an untargeted metabolomics approach to investigate the pathogenicity of Macrophomina phaseolina and Rhizopus stolonifer. Tissues from 3 different varieties of sweet potatoes namely, Beauregard-14, Beauregard-63, and Orleans were used to investigate the fungal infection. Headspace solid phase microextraction method coupled with GC/MS was used to collect the microbial volatile organic compounds (MVOCs) produced by the fungal inoculated sweet potatoes. Results analyzed using chemometric and PLS-DA analysis clearly demonstrate the differentiation of fungi infected sweet potato tissues from the healthy tissues and have identified key metabolites involved in the infection. More importantly, we have identified significantly important metabolites including groups of alcohols, alkanes, alkenes, aromatic hydrocarbons, esters, furans, ketones, organic acids, and sesquiterpenes. The metabolites are linked to cellular stress and energy metabolism pathways. Combinations of more than one chemical group improve fungal infection diagnosis. We hope these findings will lead to a sensory machine such as electronic noses for large-scale agricultural storage warehouses to identify early-stage fungal infection.

Microbial volatile biomarkers for MP charcoal rot and Rhizopus soft tissues in sweet potatoes

2019 Fall National Meeting

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